Bidirectional Association Between Diabetes and Osteoarthritis: A Population‐Based Cohort Study

BACKGROUND: Diabetes mellitus (DM) and osteoarthritis (OA) frequently coexist in middle-aged and older adults, but their longitudinal associations are mixed. This study aimed to investigate the bidirectional associations of DM with knee and hand OA (KOA and HOA) in a large population-based cohort of middle-aged and older adults. METHODS: This study utilized data from the UK Biobank. The presence and incidence of DM and OA were ascertained by participant self-reports, inpatient hospital records, primary care and death records. The associations between baseline DM and the incidence of KOA and HOA, as well as baseline KOA and HOA and the incidence of DM, were evaluated using accelerated failure time models because the proportional hazards assumption was violated. RESULTS: Among participants without KOA and HOA at baseline, baseline DM was significantly associated with earlier onset of KOA but not HOA before BMI adjustment (time ratio [TR] = 0.91, 95% confidence interval [CI] 0.87-0.95, p < 0.001), while further adjusting for BMI showed a marginal association between DM and delayed KOA onset (TR = 1.04, 95% CI: 1.00-1.09, p = 0.058) during the 13.5-year follow-up. Among participants without DM at baseline, both prevalent KOA and HOA were associated with earlier DM onset (KOA: TR = 0.91, 95% CI: 0.86-0.97, p = 0.005; HOA: TR = 0.68, 95% CI: 0.50-0.95, p = 0.021), before or after adjusting for BMI. CONCLUSION: Our findings reveal an asymmetric bidirectional link between DM and joint-specific OA. While both KOA and HOA are associated with earlier DM onset, the impact of DM on KOA is confounded or mediated by BMI, where covariate adjustment induces directional instability.